A complementary study of bonding and electronic structure of amorphous carbon films by electron spectroscopy and optical techniques

摘要

A complementary study of composition and bonding of sputtered a-C films, deposited on Si(001) substrates with various bias voltages (V_b) applied to the substrate during deposition is presented. The sp~3 and sp~2 fractions in the films were calculated by deconvolution of the X-ray photoelectron spectroscopy (XPS) Cls peak and studied by the differential auger electron spectroscopy (AES) C_(KLL) peak signal. The results of this analysis are compared with the estimation of sp~3 fraction calculated by spectroscopic ellipsometry (SE) and validated using density measurements by X-ray reflectivity. It was observed a considerable increase of sp~3 content in films deposited with negative V_b. The respective sp~3 and sp~2 fractions and Ar concentration with respect to the V_b and the depth profile analysis give valuable information on the deposition mechanism of the sputtered a-C films. XPS valence band spectra provided the electron density of states in the a-C films' valence band. The characteristic broad p band of diamond was prominent in most of the films. The valence band structure of the films was correlated with their optical response measured by SE.